The present invention relates to a flow conduit and surface enlarging means for cooling the fluid contained in the flow conduit. The invention further relates to a fuel pipe with one or more angulations for establishing flow communication between a tank and a motor installation in a vehicle, and a method for the manufacture thereof.
The fuel system in a vehicle serves to supply fuel to the motor from a tank installed in that vehicle. The fuel is pumped into an advance conduit leading to the motor. The fuel which is not consumed in the motor is extremely hot and is pumped back into the tank via a return conduit.
U.S. Pat. No. 4,479,359 teaches a conduit for heating cryogenic fluid. In particular, a heating tube comprises a cylindrical tube having both internal and external fins. The external fins comprise fins extending upwardly from the cylindrical tube. Thus, dirt may accumulate between these fins so that the heat exchanging characteristics will be reduced or vary depending on the amount of dirt accumulated in the spaces between the fins.
WO 94/23257 discloses a heat exchanger that has among its objects to cool fuel in the fuel system of a vehicle. The cooler in this arrangement has been inserted between two conduits in the return conduit. However, this cooler is very space-intensive, and in that cooler a very large loss of pressure occurs in the return conduit which means that a large pumping capacity is required to return the amount of fuel in the return conduit to the tank.
EP-0 807 756 teaches a fuel system for a vehicle wherein a tubular section is inserted. The tubular section has axially oriented cooling ribs for cooling the fuel in the advance and return conduits in the fuel system. At each of its ends, this tubular section is connected by means of tubes to the motor and tank, respectively. The tubular section comprises two parallel flow conduits and is provided with cooling ribs that allow the fuel to be cooled in a simple manner by the streams of air underneath the bottom of the vehicle.
The fuel system according to EP-0 807 756 eliminates the drawbacks in connection with pressure drops and large pumping capacity, and common tubing underneath the bottom is also utilized which saves space compared to previous designs. However, dirt may accumulate on this cooling profile that may deposit on top of and between the cooling ribs and thus reduce the cooling effect or even have an insulating effect on the profile tubing. Moreover, this known type of fuel pipe comprises mechanical joints, such as soldered joints between fuel tubing, connector tubing and cooler tubing. Such joints present: a risk of leak. This risk is greatly increased when the fuel is to be advanced in the fuel pipe under pressure. It is therefore desirable to be able to manufacture a fuel system with a minimum of joints, especially welded joints and soldered joints, in order to hereby reduce the risk of leaks occurring due to a weak joint.
In case of motors based on recently developed technology, a marked increase in the pressure and temperature of the fuel may occur. The temperature may become extremely elevated which gives rise to problems in connection with fuel tanks made of plastics and/or components in connection therewith. Likewise the fuel, such as the diesel oil, may react chemically with the plastic parts of the tank whereby the tank as well as the fuel can suffer damage. Moreover the fuel can also suffer damage such as a consequence of boiling at the elevated temperatures. In the light of this it is, in connection with such novel motor installations, of the utmost importance to cool the fuel effectively, and many producers thus require that the temperature of the fuel must be kept below a suitably low temperature.